From the "what will they think of next" department, Bina’s Audiometry is an amazingly accurate hearing test app for your iPhone.

Measuring your threshold of hearing for sounds of different frequencies, you can use it to find out the frequency range you can hear. According to the developer, most people should be able to hear up to around 15 kHz, and in general frequencies around 17 kHz and higher can usually heard only be heard by people under 20.

Audiometry is an effective hearing test that measures your threshold of hearing for sounds of different frequencies - find out just how far your ears can hear ranging frequencies.